Concerned union officials hope to strike a "delicate balance between hatching a contingency plan and respecting Weiner's continued work on MLBPA business," Passan writes.

Fehr, executive director of the NHL Players' Association since 2010, is one of several people being considered by the baseball in the event Weiner's health worsens to the point he can't handle his responsibilities as executive director. Fehr and union declined to talk to Yahoo! Sports about the report.

Fehr's long run as head of the MLBPA included five negotiations that resulted in work stoppages, including the 1994-95 strike that led the cancellation of the much of the 1994 season and the entire postseason. He led the NHLPA through this past season's lockout and earned praise for his work from his constituents.

"I certainly don’t have any plans to change," Fehr said. "I have come to respect the players both individually and as a group, more and more, every day, through this process."

Under Weiner's watch, the union signed an agreement in November for a five-year contract running until December 2016, which ensures 21 consecutive years of labor peace in Major League Baseball. The agreement allowed for blood testing for human growth hormone, introduced restraints on bonuses for amateur draft picks and international signings and restored salary arbitration eligibility for part of a class of players that lost it in the 1980s.